another question on pointers

i have come across **pointer_name before and as i decided to have a couple hours break from the poker game im writing i thought i would experiment.
what is the difference between this

Code:

---

void double_it(int *p_number)
{
    *p_number *= 2;
}

void add_three(int *p_num)
{
    *p_num += 3;
    double_it(p_num);
}
int main()
{
    int x = 1;

    add_three(&x);
    printf("x = %d\n", x);
    return 0;
}

---

and this

Code:

---

void double_it(int **p_number)
{
    **p_number *= 2;
}

void add_three(int *p_num)
{
    *p_num += 3;
    double_it(&p_num);
}
int main()
{
    int x = 1;

    add_three(&x);
    printf("x = %d\n", x);
    return 0;
}

---

both give the correct answer of 8 (or at least the one i was expecting)

i don't see the purpose of writing int **number when *number will do.
coop

Not useful here. Useful when you need to assign to a pointer within a function such that it is changed in the caller, e.g., dynamic memory allocation. That is, when an out parameter is a pointer itself.

ok thanks i think that is probably where i saw it in an example of memory request